12 men have been to the moon but only two have been to the bottom of Ocean - James Cameron wants to be third

He has commissioned Australian engineers to build a deep sea submersible which can reach the bottom of the Mariana Trench - 10.9km (36,000ft) down in the western Pacific - after deciding to set the film in the turbulent waters of Pandora, an alien moon.

The vessel will be fitted with 3D cameras designed by Cameron so that he can take unprecedented footage of such depths and, if he wants to, fill it with digitally created monsters for Avatar 2.

Cameron spent his 56th birthday in a Russian deep sea submersible called the Mir-1, descending more than 5,000ft (1.5km) into Lake Baikal in Siberia, the deepest freshwater lake in the world.

Australian scientists believed to be working for Cameron have visited the San Francisco headquarters of Hawkes Ocean Technologies, which has been building a submersible capable of settling at the bottom of the trench.

Cameron's new vessel is expected to be a two-seater, finned cylinder fitted with the latest 3D cameras and a heating system largely missing from the Trieste.

Some of his footage from the depths may end up in Avatar 2 - which is not expected to reach cinemas before 2014 - or possibly in two other deep-sea adventures that the director is considering turning into movies.